You sound like you haven’t had much experience with relationships. Certainly not enough to gain some perspective on them. You will find out that he is not nearly as perfect as he is now. You will find out that if you break up, you will be able to survive. You will find out that there will never be any certainty about the future.
When you fall in love, it creates incredibly strong feelings in you. It gives you a high that is actually higher than any drug can provide. It is instantly addicting. So the same thing that attracts you to a person makes you feel completely dependent on the person and unable to survive without them. You can not stand the idea of losing your fix.
Left alone, this high will gradually subside over time—maybe two to three years; in some cases a dozen years; and in a very few cases for a life time. Because it is gradual, you don’t really notice it so much, until you wake up some day a few years from now and wonder what happened. Then you either break up (divorce if you are married) or work to bring things back to a level that makes you both happy.
If you break up early on, then yes, it is devastating and it can take the same amount of time to recover from it as if you were following the path of a relationship that stayed together.
The thing is, you can’t worry about this. It’s too late now. You’re in the relationship. All you can do is enjoy it while it lasts, especially since, as many have pointed out, worrying about him leaving can make him leave once he gets tired of your worries. Jealousy doesn’t help, either.
If your love is real, then you should be able to talk about this. You can express your worries and work out ways for him to reassure you without it being a burden on him. If you can’t talk to him about this, then your relationship probably won’t last. The only way it will last is because you keep changing yourself into what you imagine he wants. In this way, you will become less and less yourself; less the person he fell in love with; and less the person you are. You’ll be very unhappy with yourself.
Your only choice is to be fully yourself, and to act as you would act when being fully yourself. If the relationship doesn’t work out when you do that, then it is not the relationship you thought it was.
So gain perspective on your feelings. This is normal and it will go away. If it doesn’t go away, that is a sign that something is wrong. You need to talk. If you can’t talk honestly and fully, then something is wrong.
Another thing to be very careful of is the role that fantasy plays in this. We all do this to one degree or another. In the absence of information, we imagine who a person is and what they will do under various circumstances. Sometimes we ignore information because we want our idea of the person to be who that person is.
Unfortunately or fortunately, people are usually different from who we imagine them to be. There is not much we can do to stop doing this, but we can be aware we are doing it, and try to get a reality check on our imaginations as soon as possible.
Your fantasy is that your true love will leave you and you will become a lost damsel, barely able to live. This fantasy gives you powerful feelings and makes you feel alive, even though it also makes you want to die. It is a romantic feeling. It is also pretty much unrelated to real life or to your lover.
Watch yourself. Look out for your imagination carrying you away. Get reality checks. Talk to him. About everything. And the rest, as they say, is gravy.